Family Fun

I'm 40 years old and my wife's older sister has a daughter who just turned 17. Kim and I have always been pretty close but our relationahip took a strange turn a few weeks ago. First of all let me say that Kim is a beautiful blond girl with a great body. Nice ass and tits that are 36C. She has a great smelling pussy. The reason I know this is that I have been sniffing Kim's panties and jacking off in them for the last couple of years. Other that that, nothing sexually has ever happened between us.A few week ago Kim was over visiting and my wife was out shopping. Kim knows that I am very ticklish so she walked up behind me and grabbed me in the ribs. I jumped and turned and tried to grab her but as I did she turned and I caught her by one of her firm young tits. When my hand landed on her tit she turned and backed her body up against mine. My hand stayed on her tit for several seconds. Finally I moved my hand. Nothing was said between us about it.Kim has started stopping by the house much more now. She knows when my wife is not home and she makes it a point to stop by when I am there alone. The next time she came by after that first incident she again tried to tickle me and she put herself in the same position so that I again ended up cupping her tit. This time I eased my other hand around her and held both tits in my hands, through her blouse and bra of course. Again, nothing was said.Now when Kim is around I just simply hug her and then turn her around and start playing with her tits as I stand behind her. One day last week I massaged her tits for a while and then eased my hands under her sweater, pulled her bra up off her tits, and cupped her bare tits in my hand. I pinched her hard nipples and massaged her bare tits for four or five minutes before finally stopping. All the while Kim was grinding her ass against my hard dick. Once I moved my hands, Kim turned and gave me a quick kiss on the lips. Again, nothing was said.After each or our encounters I have had to jack off 2 or 3 times just to get my dick to go down.Yesterday Kim came over and once in the house she kissed me then turned with her back against my body. I immediately pulled her sweater up and pulled her bra over her tits and started playing with her bare tits. This time I went one step farther. As my left hand massaged her beautiful young tits I ran my right hand down her stomach and under her pants and panties and cupped her hairy little pussy. I could tell as soon as my hand touched her pussy that she was extremely wet. I rubbed the outside of her pussy for a few minutes then I spread her lips and started rubbing her hard clit. In less than two minutes Kim's head leaned back against my chest and she had an orgasm like you would not believe. Slick juice poured out of her pussy and puddled in my hand when she came. I got so excited from playing with her tits and pussy and giving her an orgasm and her ass rubbing against my dick that I actually came in my pants. Still not a word was said about what happened. After it is over Kim talks about school and different things and acts like nothing has happened.I'm jacking off like crazy all the time now and I want to say something to her about what we are doing but I don't want to do anything to mess things up. Tonight is my wife and Kim's moms bridge night so I am sure Kim will come over after they leave. I am planning to go a step farther. This time I plan to pull her pants and panties down to her knees and take my hard dick out and let it rub against her bare ass while I make her cum. If anything new develops I will let you know.